// Mutex should be last field, as this field isn't copied to dump file
Updated.
2) You didn't take into account the upgrade. Saved in Postgres with
this byte and try to load in version without this byte.
The PGSS_DUMP_FILE format is defined by PGSS_FILE_HEADER magic number
(the first four bytes in the dump file). Once they does not coinside
(when the file is being read) the statistics are not loaded from the
dump file and set to zero and the irrelevant dump file is skipped. This
is the actual behaviour implemented in the code.
Respectfully,
Mikhail Litsarev,
Postgres Professional: https://postgrespro.com
From 21f579992e54d724d0c6d409c7fdf51f1c4619d7 Mon Sep 17 00:00:00 2001
From: Mikhail Litsarev <m.litsa...@postgrespro.ru>
Date: Mon, 20 Jan 2025 15:40:12 +0300
Subject: [PATCH] pg_stat_statements: improve loading and saving routines for
the dump file.
Exclude reading/writing pgssEntry mutex from/into the dump file.
Update the magic number identifying the stats file format.
---
contrib/pg_stat_statements/pg_stat_statements.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index bebf8134eb0..c52d3da1190 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -82,7 +82,7 @@ PG_MODULE_MAGIC;
#define PGSS_TEXT_FILE PG_STAT_TMP_DIR "/pgss_query_texts.stat"
/* Magic number identifying the stats file format */
-static const uint32 PGSS_FILE_HEADER = 0x20220408;
+static const uint32 PGSS_FILE_HEADER = 0x20250120;
/* PostgreSQL major version number, changes in which invalidate all entries */
static const uint32 PGSS_PG_MAJOR_VERSION = PG_VERSION_NUM / 100;
@@ -233,7 +233,11 @@ typedef struct pgssEntry
int encoding; /* query text encoding */
TimestampTz stats_since; /* timestamp of entry allocation */
TimestampTz minmax_stats_since; /* timestamp of last min/max values reset */
- slock_t mutex; /* protects the counters only */
+ /*
+ * protects the counters only. Should be the very last field, as this field
+ * isn't copied to PGSS_DUMP_FILE
+ */
+ slock_t mutex;
} pgssEntry;
/*
@@ -625,7 +629,8 @@ pgss_shmem_startup(void)
pgssEntry *entry;
Size query_offset;
- if (fread(&temp, sizeof(pgssEntry), 1, file) != 1)
+ /* Read whole pgssEntry excluding very last mutex field */
+ if (fread(&temp, offsetof(pgssEntry, mutex), 1, file) != 1)
goto read_error;
/* Encoding is the only field we can easily sanity-check */
@@ -782,7 +787,8 @@ pgss_shmem_shutdown(int code, Datum arg)
if (qstr == NULL)
continue; /* Ignore any entries with bogus texts */
- if (fwrite(entry, sizeof(pgssEntry), 1, file) != 1 ||
+ /* Write whole pgssEntry excluding very last mutex field */
+ if (fwrite(entry, offsetof(pgssEntry, mutex), 1, file) != 1 ||
fwrite(qstr, 1, len + 1, file) != len + 1)
{
/* note: we assume hash_seq_term won't change errno */
--
2.34.1
